Process for the obtaining of solutions of beryllium fluoride from double fluoride ofberyllium and of an alkali metal



Patented Feb. 26, 1935 UNITED STATES PATENT OFFICE PROCESS FOR THE OBTAINING OF SOLU- TIONS OF BERYLLIUM FLUORIDE FROM DOUBLE FLUORIDE OF BERYLLIUM OF AN ALKALI METAL No Drawing.

Serial No. 688,412. In

6 Claims.

The problem of obtaining beryllium fluoride free from sodium fluoride, starting from double fluoride of beryllium and sodium, has already formed the subject of numerous works.

Illig, I-Iosenield and Fischer, for example, indicate in a treatise entitled Investigations upon the action of crude beryls and upon the preparation of beryllium'salts suitable for electrolysis, published in Wissenschaftliche Veroffentlichungen aus dem Siemens Konzern, Vol. VIII, 1st fascicule, 1929, page 40, that they attempted, amongst others, to combine the fluoride of sodium of the BeFzNaF' with fluoride of aluminium. ,For that purpose, they melted at high temperature with the fluoride of aluminium, the double fluoride of beryllium and sodium, obtained by crystallization. They hoped that there would thus be formed, according to the reaction:-,

cryolite and fluoride of beryllium, and that when taken up with water, the BeFz would pass alone into solution, whilst the cryolite would remain insoluble and would retain the whole of the NaF. Now, the authors above mentioned ascertained that, contrary to their expectation, the fluoride of sodium remains fixed to the fluoride of beryllium and passes afresh completely into solution. They conclude from their experiments that the affinity of fluoride of sodium is greater for the fluoride of beryllium than for the fluoride of aluminium.

Contrary to the results of Illig, I-Iosenfeld and Fischer, I have found that it was very easy to combine the NaF of the double fluoride of beryllium and sodium with fluoride of aluminium. To obtain this result, it is, however, necessary not to operate by igneous fusion of the mixture of BeFzNaF and fluoride of aluminium, as was done by the previously mentioned authors, but to cause these salts to reactupon one another in the presence of water.

One may, for example, mix a solution of BeFzNaF with a solution of AlzFe, or else one may introduce into an agitated solution of A12Fs, crystallized double fluoride of beryllium and sodium. One may also introduce into a solution of BeFzNaF, solid and difficultly soluble hydrated fluoride of aluminium (A12F6.'7H2O) or again one may project into water, separately or in mixture, crystallized double fluoride of beryllium and sodium and solid and difflcultly soluble hydrated fluoride of aluminum (A12Fs.7H20). In every case, whether working at the ordinary temperature or else at a higher temperature, the NaF Application September 6, 1933,

France October 5, 1932 combines with the AlzFs in order to yield insoluble cryolite, whilst the BeFz remains or passes into solution. The solution of BeFz is afterwards separated, by decantation or filtration, from the precipitate of cryolite.

The effectiveness of rendering the Nai insoluble in the form of cryolite is greater in proportion as the quantity of AlzFc brought into operation for a given weight of NaF is greater. From this fact, the employment of fluoride of aluminium in solution is somewhat limited, because, if it be utilized in excess, this excess remains in solution with the fluoride of beryllium, which is undesirable.

The solid hydrated fluoride of aluminium- (Al2Fe.7H2O) being on the other hand very little soluble in water, one may without inconvenience employ it in great excess and thus effect a very intense insolubilization of the NaF. The excess of solid and difficultly soluble fluoride of aluminium (AlzFa'IHzO) brought into operation is eliminated with the cryolite.

The quantity of solid hydrated fluoride of auminium (AlzFa'TI-IzO), necessary to eliminate a given weight of NaF, varies moreover with the state of division of the fluoride of aluminium. The finer the particle of fluoride of aluminium, the less thereof will be necessary.

One may also combine the use of fluoride of aluminium in solution (AlzFe) and in the solid hydrated state, (AlzFa'II-IzO). One first introduces, into a solution of fluoride of aluminium, a quantity of BeFzNaF suflicient for the whole of the AlzFs to combine with the greater part of the NaF in the form of an insoluble compound which precipitates. In the solution, one has a mixture of BeFz and BeFzNaF, to which there is added solid and diflicultly soluble hydrated fluoride of aluminium (AlzFeflHzO) in quantity suflicient to precipitate almost all the NaF left in solution.

If the double fluoride of beryllium and alkali metal is available in solid form, it is advantageous to carry out the above reactions by employing, per liter of water, quantities of double fluoride of beryllium and alkali metal greater than those corresponding to the solubility of these salts in water. It is possible to obtain directly in this way concentrated solutions of beryllium fluoride. In the foregoing, one has always spoken of the compound BeFzNaF, but it is obvious that the processes described for the obtaining of BeFz free from NaF apply also to compounds containing more or less NaF per molecule of BeFz.

The following examples set out, without however limiting them, the conditions allowing of carrying out the invention.

Example 1 One heats to 70 C. a litre of solution of fluoride of aluminium having 55 grammes of AlzFs per litre, and one introduces thereinto, Whilst agitating it, 90 grammes of double fluoride of beryllium and sodium in powder form, containing 45.8% of BeFz and 52.3% of NaF (that is to say 114 parts of NaF per 106 parts of BeFz) The agitation is continued for some hours. In the solution obtained, which contains the whole of the BeFz put to use, one finds for 100 parts of BeFz, 2.7 parts of AlzFs and 14.5 parts of NaF. The effectiveness of the elimination of NaF has therefore been 87.3 per cent.

Example 2 One mixes 250 grammes of double fluoride of beryllium and sodium in powder form, containing 38.9% of EeFz and 54% of NaF (that is 138.7 parts of Na? for 100 parts of BeFz), With 660 grammes of solid and difllcultly soluble hydrated fluoride of aluminium (A12F6.'7H2O) containing 55 of AlzFs. One introduces the mixture, all at one time or in fractions, into a glass vessel furnished with a stirrer and containing 1 litre of Water.

After an agitation for a total duration of '7 hours, at ordinary temperature, one extracts on a filter under vacuum. The extracted solution contains about 82% of the Ber e employed. There is therein found for 100 parts of BeFz, 2.l parts of A12Fe and 1.6 parts of NaF. The effectiveness of the elimination of the Na? has thus been 98.8%.

The mixture of cryolite and fluoride of aluminium collected upon the filter is subjected to a methodical washing. JThere is thus recovered the whole of the BEFZ retained by these residues. The washing water is employed for a fresh operation.

Example 3 To solution of BeFz, obtained in the Ex a-mple'l and containing 14.5 parts of NaF for 100 parts of BeFz. there are added 5 grammes of solid and difficultly soluble hydrated fluoride of aluminium (A12Fe.7H20) (containing 55% of AlzFs per gramme of NaF in solution. After of solid hydrate (AlzFa.7H2O) thoroughly eliminates the NaF of the double fluoride of beryllium and sodium. If Illig, Hosenfeld and Fischer have not obtained this result, by melting together fluoride of aliuninum and double fluoride of beryllium and sodium, and then recovering by Water the product of the fusion, it is because these authors worked with a fusion. This fusion caused the fluoride of aluminum to be in the anhydride state, at the time when the recovery by water was attempted. The fluoride of aluminum in the anhydride state is insoluble in the water used in the attempt to dissolve any BeFz.

What I claim is:

l. A process for the obtaining of aqueous solutions of fluoride of beryllium from a double fluoride of beryllium and of an alkali metal, consisting intreating the said double fluoride in an aqueous medium by hydrated fluoride of aluminium.

'2. A process for the obtaining of aqueous solutions of fluoride of beryllium from a double fluoride of beryllium and of an alkali metal, consisting in bringing together the said double fluoride inan aqueous medium with a solid and difficultly soluble hydrated fluoride of aluminium (AlzFe. ll-I20) 3. A process for the obtaining of aqueous solutions of fluoride of beryllium from a double fluoride of beryllium and of an alkali metal, consisting in treating the said double fluoride in the crystallized state in an aqueous medium by hydrated fluoride of aluminium.

4. A process for the obtaining of aqueous solutions or fluoride of berylliiun. from a double fluoride of beryllium and of an alkali metal, consisting in treating the said double fluoride in the dissolved state in an aqueous medium by hydrated fluoride of aluminium.

5. A process for the obtaining ofaqueous solutions of fluoride of beryllium from a double fluor ide oi beryllium and of an alkali metal, consisting in adding the said double fluoride and the solid and diificultly soluble hydrated fluoride of aluminium (Al2Fe.7HzO),tl1e latter in excess, both in the solid state, to a quantity of water less than that which would be necessary to dissolve the double fluoride of beryllium and alkali metal.

6. A process for the obtaining of aqueous solutions of fluoride of beryllium from a double fluoride of beryllium and of an alkali metal, consisting in first adding to the double fluoride a quantity of a solution of aluminium fluoride (AlzFt) insuihcient for rendering insoluble the alkali fluoride of the double fluoride brought into operation, and then adding solid and diflicultly soluble hydrated fluoride of aluminium (A12Fs.7H20) for rendering insoluble the alkali fluoride left in solution.

MAURICE BEJA. 

